Pulse Oximetry
Pulse oximetry1,2 is a non-invasive continuous method for monitoring the oxygenation level of a patient's hemoglobin (Hb) in the arterial system.

Pulse oximetry is based on two physical principles: (a) arterial blood generates a pulsatile signal (hence the name "pulse oximetry"), which distinguishes it from surrounding tissue; and (b) oxygen-bound Hb (HbO2) and reduced Hb have different absorption spectra: in the red region, HbO2 absorbs less light than Hb, while the reverse occurs in the infrared region.

Pulse oximetry has become a standard of care in the operating and recovery rooms, intensive care units (ICUs) and emergency services. For example, pulse oximetry revealed that in more than 80% of the cases, patients in the acute Admissions Unit had saturations of <85% for at least 1 hour3. Documented hypoxia to this degree can cause significant cardiac and cerebral malfunction. When patients are sedated for procedures such as endoscopy, oximetry has been shown to increase safety by alerting the staff to unexpected hypoxia.

Due to its widespread use, it is important to note that pulse oximetry is known to provide erroneous oxygen saturation readings under certain conditions. For example, false readings may be caused by hypoperfusion of the extremity being used for monitoring (due to hypovolemia, hypothermia, low cardiac output, drug-induced vasoconstriction etc.). In these cases, the low amplitude of the signal becomes hard to distinguish from background noise.

The NBM-200MP system utilizes OrSense's proprietary occlusion spectroscopy technology, a novel and improved method for measuring Oxygen Saturation. The system therefore offers non-invasive, continuous and accurate measurement of oxygen saturation in states of hypovolemia, hypothermia and vasoconstriction, as well as during regular perfusion. In addition to oxygen saturation, the system provides Hemoglobin (Hb) values. The NBM-200MP’s superior performance was validated by multi-center trials in the United States and Europe.

References:
1. Pulse oximetry. Fearnley S.J. (1995). Update in Anaesthesia Issue 5, article 2.
2. Pulse oximetry. Jubran A. (1999). Critical Care 3: R11-R17
3. Is Hypoxia common despite oxygen treatment in the Acute Medical Ward? Dhar R, Harrison RN, Snashall PD. (2006) Internet Journal of Medical update 1(2): http://www.geocities.com/agnihotrimed/paper01_jul-dec2006.htm